Silane-based moisture curable compositions are known for providing good adherence to certain substrates, e.g. glass or metal, once these compositions are fully cured. However, such compositions are liquid or pasty in their uncured state and provide little or no green strength i.e., the initial mechanical strength developed prior to when significant curing takes place.
Polyurethane reactive hot melts provide excellent green strengths but typically do not provide acceptable adhesion to substrates such as glass and metal. Many polyurethane reactive hot melts also suffer from blistering during cure.
Prior methods of enhancing initial green strength, open times and tack strength in hot melts have focused on the inclusion of various additives, such as various blends of different types and molecular weights of components used in polyurethane prepolymer formulations, or the addition of tackifiers such as thermoplastics to the thus formed polyurethane prepolymers.
While some of these prior methods have proved useful in some instances, their result for many applications have not been entirely satisfactory.
Thus, there is a need for a silane-reactive moisture-curing hot melt which overcomes the disadvantages of the prior art and exhibits improved (longer) open time, high green strength and enhanced tack strength, excellent UV and non-blistering resistance. Moreover, it would be desirable to have a silane-reactive moisture curing composition which has excellent adhesion to glass and metal and which exhibits excellent weather resistance while still maintaining acceptable mechanical, solvent resistance and other physical and chemical advantages known to hot melt compositions.